In the essential fatty acid (EFA) deficient epidermal skin disease, lack of the dietary essential fatty acids 18 2 and 20 4 (n-6) results in a hyperproliferative epidermis through an as yet unknown mechanism. The hypothesis driving this proposal is that the fatty acid content of membrane phospholipids controls the viscosity (fluidity) of the cell membrane and that is parameter, in turn, affects membrane mechanisms that control cell function. The long-term objective of the proposed studies is to determine the mechanism of membrane phospholipid fatty acid regulation of keratinocyte function. The EFA deficient keratinocytes will be grown in essential fatty acid regulation of keratinocyte function. The EFA deficient keratinocytes will be grown in essential fatty acid supplemented medium to yield cells with "normalized" membranes. The EFA deficient cell model, the "normalization" of their phospholipid fatty acid content and successful measurements of membrane viscosity have been reported by us. Thus, it is proposed to use biochemical methods (GC, HPLC and Radiomatic analysis) in conjunction with electron paramagnetic resonance (EPR), Fluorescence Recovery experiments, and extensive data reductions to address the following specific aims a) test the hypothesis that changes in membrane fluidity caused by altered phospholipid fatty acid content effects the kinetic rates of membrane associated enzymes b) understand the effect of altered fatty acid phospholipid content (GC) on membrane viscosity (EPR) resulting from supplementing the growth medium with various fatty acids. Long term and short term studies will be done using various essential fatty acids, the monounsaturated fatty acid 19 1, and eicosanoids such as PGE2 c) determine the effect of dermatologically effective drugs on EFA deficient and normalized keratinocytes. The effect of these drugs on cell growth and differentiation will be assessed. The phospholipid fatty acid content and plasma membrane viscosity cells will be determined and the role of 20 4 and eicosanoids will be studied d) analyze second messenger and signaling systems in EFA deficient and fatty acid normalized cells. These will be studies of 1) membrane viscosity and the mobility of epidermal growth factor receptor by fluorescence recovery of photobleaching experiments. 2) the cyclic AMP and cyclic GMP systems (response to agonist) and enzyme activity in EFA deficient and fatty acids normalized keratinocytes. 3) phospholipase A2 and phospholipase C enzyme activity. Understanding these basic mechanisms will expand our knowledge of epidermal function and diseases states.